1. Field of the Invention
The present invention relates to a method and apparatus for providing a high-quality representation of a volume having a real-time reconstruction therein of movement of an object, wherein the real-time movement of the object is determined using a lower-quality representation of a portion of the volume.
2. Background of the Invention
3-D angiography is a relatively new application of an X-ray interventional procedure that utilizes a rotational run of an X-ray apparatus to acquire a series of 2-D X-ray projections along a circular (or almost circular) orbit. The rotational run is acquired by moving an X-ray source and an Image Intensifier (II) camera mounted on a rotatable C-arm about a patient, while a continuous injection of contrast bolus is administered into the vasculature of the patient. The rotational series of 2-D image data is then sent to a cone beam reconstruction process, which generates a 3-D reconstruction of the patient""s vascular structure.
The vascular structures depicted in the 3-D reconstructed images are then studied by the clinicians in order to plan an interventional procedure (operation). Once the plan is determined, catheters are used to carry out what is called an endovascular procedure. The entire procedure is constantly monitored by the clinicians under the guidance of a 2-D fluoroscopic imaging procedure. The 2-D fluoroscopic imaging procedure uses the same imaging apparatus and patient positioning as was used to perform the 3-D angiography procedure. Before starting the intervention, the clinician studies the previously acquired 3-D vasculature structures in order to choose an optimum way to place the C-arm to generate the best 2-D fluoroscopic image, thereby maximizing the ability of the 2-D procedure to aid in guiding the catheters during the operation.
Accordingly, the X-ray fluoroscopic image is used as a navigation tool by the clinicians to aid maneuvering the catheters through tortuous paths of the patient""s vasculature. Every once-in-a-while the clinicians must inject contrast material to opacify the vessel so that the vessel can be seen under the 2-D fluoroscopic imaging procedure. It is also common current practice to capture and store a contrast-enhanced fluoroscopic image, and then subtract that image from subsequent images. This results in a static display of the vascular structures (displayed in white), while the live (real-time) catheter appears in black. This procedure is known as xe2x80x9croad mappingxe2x80x9d. The roadmap is a 2-D projection of the vascular structures, and like any 2-D projection of a 3-D body has substantial positional ambiguity.
It is an object of the present invention to provide a more accurate real-time representation of the movement of an object in a volume when a previously acquired high-quality static representation of the volume is available but only a lower-quality real-time representation is available for detecting movement of the object.
It is a further object of the present invention to provide a method and apparatus which combines real-time 2-D fluoroscopic images with previously acquired and stored 3-D reconstructed image data.
A still further aspect of the invention is to provide a method and apparatus for determining the coordinate transformations needed to xe2x80x9cco-registerxe2x80x9d or merge a stored 3-D representation of a volume with a real-time 2-D representation of a portion of the volume.
A still further object of the present invention is to provide a method and apparatus for operating medical imaging equipment so as to specifically acquire xe2x80x9canatomical landmarksxe2x80x9d, which are used to develop the coordinate transformations needed to co-register stored and real-time representations of the volume. More specifically, a magnetic resonance angiography procedure can be specifically performed in order to develop anatomical landmark which are then used for co-registering the related landmarks in a 3-D angiography representation.
Described is an imaging apparatus for providing a high-quality representation of a volume having a real-time 3-D reconstruction therein of a movement of an object. The real-time movement of the object is determined using a lower-quality representation of only a portion of the volume. The inventive apparatus comprises first means for acquiring a low resolution image displaying at least one anatomical landmark, means for co-registering the low resolution image with a pre-stored high resolution reconstruction image on a basis of at least one anatomical landmark; second means for acquiring a low resolution real-time 2-D projection image; and means for reconstructing a real-time movement of the object in the high resolution reconstruction image.